NERVOUS SYSTEM OF THE TUNICATE 317 



that siphon, but also the closure of the other siphon as well. 

 The unstimulated siphon did not always respond, owing ap- 

 parently to the exhausted condition of the ganglion which 

 seemed to fatigue quickly with too frequent an application of 

 the stimulus. As no method was employed either for measuring 

 the strength of the stimulus or for graphically recording the 

 response, no exact comparison could be made between the 

 original normal responses and those subsequent to regeneration 

 of the ganglion. The sensitivity of the animal as a whole, how- 

 ever, did not seem so great after the restoration of ganglionic 

 tissues as before the ganglion had been extirpated, for although 

 the siphons responded readily to feeble penciling with a camel' s- 

 hair brush, they did not respond to vibratory disturbances, such 

 as the shutting of doors and the treading of feet. This in- 

 ability to respond to vibrations may find its explanation in the 

 ease with which the ganglion is fatigued, because, even though 

 the gangUon were composed of nervous tissue of a higher degree 

 of sensitivity than before, the depressing effect of frequent vibra- 

 tory stimulations would prevent the state of irritability from 

 attaining to a maximum. The latent period between the re- 

 sponses of the in- and excurrent siphons was not measured, but 

 it was about one-quarter to one-half second. 



Just what the histological condition of the ganglion is at the 

 time of restoration of the power of coordination it would be of 

 interest to know. The neurogenesis, however, of the regenerat- 

 ing ganglion and its relation to restoration of physiological 

 function is a problem which still awaits investigation. 



REACTION OF ASCIDIA MENTULA TO CHEMICAL SUBSTANCES 



While the following are but a few incidental tests of a tentative 

 nature, they throw a little light on the chemical sense of the 

 animal. In the work of Hecht ('18) will be found an intensive 

 treatment of the reactions of Ascidia atra to chemicals. 



Needle-like crystals of quinine (| mm. in length) were dropped 

 on to the oral tentacles of three animals. After lying on them 

 for a moment or two, they were ejected. A thread, knotted on 



